1. Field of the Invention
The present invention relates to a process for making small particle size silver chloride (AgCl). In particular, the present invention relates to a process for making small Particle size silver chloride by reacting silver metal particles with chlorine gas in a chlorine-stable organic solvent.
2. Brief Description of Relevant Art
Small size silver chloride (AgCl) particles are commonly used as a component in making silver/silver chloride conductive pastes. Such pastes are used in making human contact electrodes, such as those used for measuring cardiovascular activity. See U.S. Pat. No. 4,877,512, which issued to Bowns and Diepholz on Oct. 31, 1989 and is incorporated herein by reference in its entirety.
Small-size silver chloride particles have been conventionally prepared by reaction of silver nitrate with hydrochloride acid. The product made by this process has the disadvantage of being relatively expensive, owing to the high cost of the silver nitrate starting material. Silver chloride has also been made by passing gaseous chlorine over silver metal powder. It has been found that when this latter method is employed, the resulting silver chloride particles commonly agglomerate or fuse together. The thus-formed large size silver chloride particles are formed by the accompanying large heat of reaction and cannot be used in the above-noted conductive pastes. Instead, it is necessary to grind and screen those particles down to a suitable size. Such grinding and screening is time consuming and may greatly increase the cost of the resulting silver chloride product.
Accordingly, there is a need for a new, inexpensive process for making small-size silver chloride particles. It is believed that the present invention is a solution to that need.